JPH03223559A - Hourglass worm gear - Google Patents

Abstract

PURPOSE:To enhance both load ability and efficiency as well as to prevent contact configuration from deteriorating, and also prevent an effective tooth surface from being reduced in area by assembling an hourglass worm gear which is created by a tooth surface grinding stone having a specified circular arc radius, at the center distance of the worm gear, and thereby widening an effective meshing range. CONSTITUTION:An hourglass worm gear is assembled in, which is created by a tooth surface grinding stone the contour of which is formed by a circular arc radius (r) wherein (r)=(-0.3 through 1.0)X(e), and (e) represents the center distance of the worm gear, and an effective meshing range is widened so that loading ability is thereby enhanced. As a result, it is possible to enlarge the angle formed by a concurrent contact line and relative velocity, and a lubricating film is thickened so that securing high efficiency can be expected. This thereby prevents contact configuration from deteriorating and also prevents an effective tooth surface from being reduced in area at the time of loading. By this constitution, high strength materials excellent in mechanical properties can be used for a worm wheel member, and load ability can thereby be enhanced much more.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a worm gear used in a worm reducer or the like.

[Conventional technology]

The worm gear of the prior art has a contact form as shown in FIG. 7(a), and the ineffective tooth surface portion shown by hatching occupies the vicinity of the center of the worm tooth portion.

The conventional drum-shaped worm gear has a contact form like that shown in FIG.

The shape of the grindstone for grinding the tooth surface of the drum-shaped worm is as shown in FIG.

There is also a method in which the grindstone is shaped like a cone and the bottom surface of the cone is used, as shown in FIG.

In Figures 8 and 9, 01 is a warm material.

02 is a conical grindstone, 03 is a grindstone driving motor, and 04 is a conical bottom grindstone.

[Problem to be solved by the invention]

(11) The contact surface pressure and lubricating oil film thickness on the tooth surfaces that affect the performance of the worm gear are determined by the following factors: ■ the length of the simultaneous contact line of the worm gear mesh, ■ the relative curvature at the contact point, and ■ the angle between the contact line and the relative velocity direction. ruled by.

(2) In the conventional technology, it is difficult to make improvements focusing on the above items (1) to (2) because there is no degree of freedom in the shape of the grindstone that creates the tooth profile.

(3) Furthermore, when a drum-shaped worm gear with an irregular lead and an irregular pressure angle on the worm screen is subjected to a high load, the above-mentioned contact form deteriorates due to the influence of shaft displacement due to K, such as deformation of the bearing part, resulting in high performance. (high efficiency, high load capacity).

(4) For this reason, the materials for worm gears are generally
Case-hardened copper is used for the worm side, and a material with high compatibility and therefore low strength is used for the worm foil side (
Example: Material name PBC2, AlBO2, etc., hardness HB 100
around HB150), the load capacity is reduced.

Furthermore, engineering plastics cannot be used as the material for the worm gear.

[Means to solve the problem]

(1) The shape of the grinding wheel for grinding the tooth surface of the drum-shaped worm is an arc, the radius r of the arc is given a degree of freedom, and an ideal contact form is obtained by controlling this r.

(2) In order to ensure an ideal contact form for shaft displacement of 11 m under high load conditions, the tooth profile of the worm gear with little tooth contact change was adjusted according to the above-mentioned arc radius r control and gear cutting specifications. By controlling and creating.

[Effect]

(1) It is possible to widen the effective meshing range and improve load capacity.

(2) The angle formed by the simultaneous contact line and the relative speed is made thicker (and the thickness of the lubricating oil film can be increased, and highly effective forces can be expected).

(3) It becomes possible to arbitrarily control the contact form.

[First embodiment] In Figs. 1 to 4, A1 is the worm axis A2: Wheel axis A3 is the tool axis A: Grinding wheel axis ω1 is the worm angular velocity ω2: Wheel angular velocity ω3
The angular velocity 1 of the tool is the speed ratio of the worm and the wheel (=lω11/1ω21
) Q is the cross section of the whetstone shaft, and the center Sc of the arc is the cross section of the whetstone shaft, the arc Scu! The radius e of Sc is the center distance of the worm gear.

(No. 11 worm is created by a grindstone having a torus surface on the grindstone surface. In that case, as shown in Fig. 1, the tool axis A3
is located at the same location as the wheel axis A2, and the relative movement between the tool and the workpiece worm ω3. ω, is the relative motion between the wheel and the worm ω2. Match ω1. (Figure 2) (2) The wheel is created on a hob having the same basic curved surface as the worm surface.

(3) The drum-shaped worm gear set in this way has two contact lines: the original contact line between the worm and the grinding wheel (first contact), and the contact line (second contact Aljl) caused by two contacts between the worm. This is a two-line contact that contacts along The shape is basically the same as the worm gear.

(4) Here, the worm tooth flank is divided into two regions by this limit normal point curve, one of which becomes an invalid tooth flank portion. For a worm gear perpendicular to the axis, this curve intersects the common perpendicular of the worm and wheel axes. A feature of the present invention is that this intersection can be moved as far as possible outside the effective meshing range and in the worm axis direction, thereby making it possible to widen the meshing range.

(5) Design example Gear specifications for reduction ratio: 1=40 are shown in Table 1.

The results of analyzing the contact form and changes in tooth contact under load by changing the grindstone arc diameter r will be described below, including a comparison with the prior art.

Figure 3 shows the trajectory of the contact line (1=40), where r=
-0,2 (Fig. 3 ←→), the limit normal point curve moves away in the worm axis direction, proving that the effective meshing range expands.

Furthermore, when r=-0,2 (Fig. 3←-1), the contact line from the throat of the worm wheel to the end of engagement forms a large angle with respect to the II line direction.

In addition, in FIG. 3, ■~■, φ~(3) are numbers of contact lines.

In most conventional drum-shaped worm gears, the limit normal point curve passes from the center of the worm engagement to the exit, from the tooth bottom to the tooth tip (see Figure 7 (a)).
A part of the area on the worm tooth surface became an invalid tooth surface, and the meshing range was limited.

Furthermore, there are few cases in which the reed contact at the end of meshing has a large angle with respect to the relative speed direction.

Next, when the gear specifications are shown in Table 2, the analysis results regarding changes in the tooth contact 9 under load are shown in FIG.

Table 1. When the wheel is loaded, the worm moves by .mu.m parallel to the rotation axis at the normal position toward the beginning of the force interaction, and there is an axial displacement in which the center distance of the worm gear (el) moves by 6 .mu.m. Assuming this, in the grindstone arc r-02, about 45 inches of the regular total tooth contact area is secured as the tooth contact area, but in the conventional drum-shaped worm gear, this is less than 10% of the regular tooth contact area.

In addition, in Table 2, A: non-linear arc toothed drum-shaped worm gear r according to the present invention.
== 0.2e B: Non-linear arc-shaped drum-shaped worm gear r=
-0,2+ C: Conventional hourglass-shaped worm gear...The one in Figure 8 D: The conventional hourglass-shaped worm gear...The one in Figure 9 Also, in Figure 4, the black colored part indicates the tooth contact part, and the shoulder indicates the tooth number of the worm wheel.

[Second Embodiment] In Figs. 5 and 6, A is the worm shaft, A2 is the wheel axis, A3 is the tool axis, A is the grindstone axis Q is the center of the arc of the grindstone shaft cross section, Sc is the center of the arc of the grindstone shaft cross section, SQ is the grindstone axis. The locus r created by point Q around the radius φ1. ω is the rotation angle of the worm and the angular velocity φ2. ω2 is the rotation angle of the wheel, and the angular velocity φ3. ω3 is the rotation angle of the tool, and the angular velocity 1 is ω1/ω2 φ1=f3□φ3+f3□φ2 ” f33φ3.

The worm tooth surface is created by a grindstone having a torus surface whose axial cross section is a circular arc on the grindstone surface, as in the first embodiment.

A shift true speed method is adopted in which the rotation ratio of the tool axis and the workpiece worm axis as well as the distance between the axes when creating the worm tooth surface are changed from those given by the gear specifications.

Also, when creating the worm tooth surface, the rotation ratio of both the worm and tool axes is continuously changed to create the tooth surface.

The worm wheel tooth surface uses a hob whose basic curved surface is the same as the worm tooth surface, and the center distance 1 is the same as the gear specifications.
It is created by the rotation ratio (Figure 5).

In the worm gear designed according to the gear cutting principle described above, the projection group of the tooth surface normal lines set at the contact point onto a plane perpendicular to the worm wheel axis passes through the center of rotation of the shaft displacement under load. In addition, it is possible to adjust the contact area so that it passes through a narrow area near the center of rotation, and it is possible to prevent the tooth contact area from becoming narrower under load.

The specifications of the gear and gear cutter in the second embodiment are shown in Table 3. Table 3 shows the shaft displacement under load. The results of analyzing the tooth contact assuming that the tooth moves by 5 μm in the direction of increasing distance are shown with no displacement (regular tooth contact).
The case is shown in FIG. 6.

As is clear from FIG. 6, in the second embodiment of the present invention,
An effective tooth contact area of 70 to 80 inches can be secured.

In FIG. 6, the black colored part indicates the contact part, and the numbers indicate the tooth numbers of the worm wheel.

[Third Embodiment] With this tooth profile, the working surface pressure can be reduced to a small percentage of that of the conventional tooth profile, so engineering plastics (eg Me nylon) can be used as the worm wheel material, and the following effects can be expected.

(However, the worm gear size is the same as the conventional one.) (a) - No lubrication possible (b) Low noise (conventional 7 oaB (#→ this example 45 dB)
(C) Light weight (compared to the conventional one) Cost reduction (1/2 compared to the conventional one) [Effects of the invention] The circular arc-toothed hourglass-shaped worm gear according to the present invention has a worm gear center distance θ where r=(− By incorporating a drum-shaped worm created by a tooth surface grinding wheel with an arc radius of 0.3 to 1.0)e, the following effects are achieved.

(11) It is possible to widen the effective meshing range and improve load capacity.

(2) The angle between the simultaneous contact line and the relative speed can be made thicker, the lubricating oil film can be thicker, and high efficiency can be expected.

(3) Deterioration of contact form and reduction of effective tooth contact area can be prevented during loading. (Regular - 80 inches of area can be secured) (4) According to the above (1), +2), and (3),
As the worm wheel material, it becomes possible to use a high-strength material with excellent mechanical properties, and the load capacity can be further improved.

For example, as a worm wheel material, the hardness is HB200~3.
00 copper alloy or steel can be used.

Furthermore, engineering plastics can be used as the worm wheel material.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the initial position of the grinding wheel tool relative to the gear in the first embodiment of the present invention, FIG. 2 is a diagram showing the positions of the main specifications of the grinding wheel surface, and FIG. Fig. 4 is a diagram of the tooth contact analysis results of the present invention and prior art; Fig. 5 is a diagram of gear cutting conditions and settings according to the second embodiment; Fig. 6 is a diagram of the trajectory;
The figure is a diagram of the same tooth contact analysis as above, and Figures 7 (a) and (b) are diagrams of the contact form of the worm and wheel according to the conventional technology.
FIG. 8 is a layout diagram of a conical grindstone according to the prior art, and FIG. 9 is a layout diagram of a conical bottom grindstone according to the prior art. A1...Worm axis l A2...Wheel axis. A3...Tool axis, A...Wheelstone axis. ω1... Angular velocity of the worm, ω2... Angular velocity of the wheel. ←)...The center distance of the worm gear.

Claims (1)

[Claims] For the center distance e of the worm gear, r = (-0.3 to 1
．． 0) An hourglass-shaped worm gear characterized by incorporating an hourglass-shaped worm created by a tooth surface grinding wheel having a cross-sectional shape with an arcuate radius of e to expand the effective meshing range and improve load capacity.